Polymer composition



United States Patent 3,417,045 POLYMER COMPOSITION Walter A. Henson andRobert L. Zimmerman, Midland,

Mich., assignors to The Dow Chemical Company, Midland, Mich., acorporation of Delaware No Drawing. Continuation-impart of applicationSer. No. 97,730, Mar. 23, 1961. This application Aug. 19, 1966, Ser. No.573,486

16 Claims. (Cl. 260-33.6)

ABSTRACT OF THE DISCLOSURE This application relates to epoxycompositions containing homogenous copolymers of vinyl aromaticcompounds and an a,/3-unsaturated dicarboxylic acid or an hydride whichare useful in coatings and laminates.

The present invention relates to polymer compositions and is moreparticularly concerned with heat-converted protective and decorativecoatings of thermosetting compositions of homogenous copolymers of vinylaromatic compounds with a,fl-unsaturated dicarboxylic acids oranhydrides and epoxy compounds, for machines, household appliances,automotive equipment, tools, metal panels, moldings, laminates, and thelike. This application is a continuation-in-part of our copendingapplication Ser. No. 462,711 filed June 9, 1965 which was in turn acontinuation-in-part-of Ser. No. 97,730 filed Mar. 23, 1961 which is nowabandoned.

We have discovered that hard, tough, glossy, transparent and adherentcontinuous coatings and laminates may be produced by forming an intimatemixture of (A) a homogenous copolymer of (1) from 99 to 65 parts,preferably from 97 to 80 parts by weight of a vinyl aromatic compound,and, correspondingly, (2) from 1 to 35, preferably from 3 to 20 weightpercent of an a,}8-unsaturated dicarboxylic acid or anhydride, and (B)an epoxide having an epoxide equivalent weight of between 44 and 1000,preferably between 70 and 550, in a ratio to the vinyl aromaticcopolymer such that the epoxide to anhydride, or anhydride plus COOH,ratio is between 0.2 and 2.5, advantageously from 0.5 to 2.0, preferablyin an organic solvent with or without an added catalyst, applying thisresin solution to a substrate and baking to cause a curing reaction. Itis preferred that the thermosetting composition contain at least 60parts by weight of the vinyl aromatic copolymer.

It is desirable that the copolymer have a molecular weight characterizedby 10 percent solution viscosity in methyl ethyl ketone at 25 C. of 0.5to 20 cps., preferably 0.9 to 10 cps.

Homogenous refers to copolymer composition homogeneity. Such copolymersare essentially gel-free and transparent, that is, optical transmissionis above 80 percent.

By fractional precipitation methods the homogeneous copolymers are shownto have an essentially uniform copolymer distribution, that is, at least90 percent of the copolymer will have an unsaturated anhydride componentcomposition which does not vary more than percent, with best samples notvarying more than 2 percent.

Vinyl aromatic compounds which are suitable include, for example,styrene, vinyltoluene, t-butyl styrene, chlorostyrene, dichlorostyrene,u-methyl styrene, vinyl Xylene and the like.

o s-Unsaturated dicarboxylic acids or anhydrides which are suitableinclude, for example, maleic anhydride, chloromaleic anhydride,citraconic anhydride, itaconic an- 3,417,045 Patented Dec. 17, 1968 "icehydride, aconitic anhydride, fumaric acid, itaconic acid and the like.

Copolymers useful in the present invention are preferably prepared fromthe vinyl aromatic monomer and acid anhydride by solutionpolymerization, although bulk polymerization methods may also beemployed. Two requirements of the polymerization method are (1) that itresults in relatively uniform copolymer composition, and (2) that thecopolymer be essentially uncrosslinked.

The preferable route, however, is to prepare the anhydride containingcopolymer as described in U.S. Patent 3,336,267 issued Aug. 15, 1967.This reaction is advantageously carried out in an aromatic or ketonicsolvent or solvent blend.

While the invention is applicable to epoxides, i.e., three memberheterocycles containing one oxygen and two carbon atoms, generally,preferred polyepoxides are glycidyl polyethers of aromatic polyhydriccompounds having epoxide equivalent Weights of to 550. Glycidyl ethersof polyhydric alcohols are also well known. These polyepoxides are madeby reacting at least about two mols of an epihalohydrin with one mol ofa polyhydric alcohol such as ethylene glycol, pentaerythritol, etc.,followed by dehydrohalogenation according to US. Patent 2,581,565.

In addition to polyepoxides made from alcohols or phenols and anepihalohydrin, polyepoxides made by the known peracid method are alsosuitable. Epoxides of unsaturated esters, polyesters, diolefins, and thelike can be prepared by reacting the unsaturated compound with aperacid. The reaction is one of epoxidation of compounds with isolateddouble bonds, at a temperature sufficiently low so that the acidresulting from the peracid, for example, acetic acid in the case ofperacetic acid, does not react with the resulting epoxide group to formhydroxyl groups and ester linkages. Preparation of polyepoxides by theperacid method is described in various periodicals and patents and suchcompounds as butadiene, cyclic olefins, ethyl linoleate, as well as diortri-unsaturated drying oils or drying oil acids, esters and polyesterscan all be converted to polyepoxides.

Epoxidized drying oils are also well known, these polyepoxides usuallybeing prepared by reaction of a peracid such as peracetic acid orper-formic acid with the unsaturated drying oil according to US. Patent2,569,502.

Desirable esters for epoxidation are prepared by reacting unsaturatedaldehydes with butadiene to form unsaturated cyclic aldehydes. These canbe condensed by the Tischenko reaction to form esters or reduced to formalcohols which can be subsequently reacted with acids from esters.

' In addition to epoxidized drying oils, butadiene dioxide and monomericesters, polymeric esters can also be epoxidized by the peracid method asdescribed in Australian Patent 11,862, 1955. Examples of theseunsaturated polyesters are those made from unsaturated polyhydricalcohols and unsaturated polybasic acids, for example, maleic acid,Z-butenedioic acid, 4-cyclohexene- 1,2-dicarboxylic acid, dimerizedlinoleic acid, etc., and such alcohols as ethylene glycol,1,6-hexanediol, 3-ethylhexanediol-1,3-pentaerythritol, etc. Otherpolyesters which can be epoxidized with pcracetic or other peracids aremade from saturated acids and unsaturated alcohols, for exam-ple,2-butenediol-l,4; 1,5-hexanediene-3,4-diol; pentene-1,5-diol,cyclohexanediol-2,5; etc., reacted with such saturated acids or acidanhydrides as malonic, succinic, glutaric, terephthalic, etc.

Examples of such polyepoxides include the diglycidyl ether of diethyleneglycol or dipropylene glycol, the

diglycidyl ether of polypropylene glycols having molecular weights upto, for example, about 2000, the triglycidyl ether of glycerine,bisphenolic epoxies, epoxy novolacs, glycidyl ethers of Cashew nut oil,epoxidized soybean oil, epoxidized unsaturated polyesters, vinylcyclohexene dioxide, dicyclopentadiene, dioxide, dipentene dioxide,epoxidized polybutadiene and epoxidized aldehyde condensates such as3,4-epoxy-6-methylcyclohexylmethyl-3,4- epoxy-6-rnethylcyclohexanecarboxylate.

Monoepoxides which are suitable include 3,4-epoxy-6-methylcyclohexylmethyl acetate; 2,3 epoxy 2 ethylhexanol;allyl-9-10-epoxystearate; 1,2-diisobutylene oxid triisobutylene oxide;styrene oxide; epichlorohydrin; butyl glycidyl ether, butylene oxide,propylene oxide, ethylene oxide, glycidol and the like. When employingthe lower boiling epoxides it is preferable to use pressure when curing,although, if desired, curing may be carried out at room temperature forsomewhat longer periods of time.

Curing catalysts such as tertiary amines or amine salts, quaternaryamine bases or salts, or inorganic bases may be used, if desired, toshorten the curing time.

The compositions of the present invention may include other additivessuch as plasticizers, fillers, pigments and the like. If desired,reactive agents such as epoxy, hydroxy, carboxy, anhydride, andmercapto-containing agents may be employed to obtain desired effects.Examples of such agents include polyesters made from phthalic or adipicacid and ethylene glycol or glycerine; anhydrides such as dodecylsuccinic anhydride and trimellitic anhydride; and liquid mercaptanterminated polysulfide polymers. Non-reactive plasticizers and additivessuch as n-butyl stearate, dioctyl diphenyl oxides, tris butyl phenylphosphate; glass, cellulosic or synthetic fibers; metal fillings,pigments, and inorganic fillers may be added as desired.

Coating and laminating applications normally employ organic solventsolutions of the copolymer-epoxy compositions. The solvent or solventblend employed is chosen to provide the desired volatility, viscosity,rheology, sprayability and/ or other properties.

Solvents which are suitable include aromatic hydrocarbons such astoluene and xylene, ketones such as methyl ethyl ketone, methyl isobutylketone, diacetone alcohol, and mesitylene oxide, high solvency naphthas,mineral spirits and alcohols, although mineral spirits must normally beused with another solvent and the alcohols are not generally preferredbecause of their reactivity with the anhydride in the polymer.

Inasmuch as aromatic hydrocarbons provide economic solvents for theresins of this invention, a particular advantage is gained by using lessthan 20 mole percent of maleic anhydride in the vinyl copolymer. Withgreater amounts than this, solvent blends are usually required todissolve the resin and higher viscosity solutions generally result. Inaddition, at higher maleic content th amount of epoxy resin required toreact with the ca boxyl groups becomes greater and can lead to ovecrosslinking as well as economic disadvantages.

Compositions of this invention may, if desired, be prepared in anaqueous medium by converting the vinyl aromatic a,fi-unsaturateddicarboxylic acid copolymers, preferably those containing between 10 and35, more desirably those containing between and weight percent of theacid, to a water-soluble salt and dispersing the epoxy compound therein.

The polyepoxy used to cure or thermoset the vinyl copolymer resin alsoimparts improved adhesion to a substrate such as glass, metal, wood,etc. This allows even very hard thermoset composition to exhibit goodimpact resistance and flexibility in that although crazing may occur, acoating, for example, will still adhere. Flexibility may be attained byincorporating plasticizing additives or by choosing a flexible typepolyepoxy or a mixture thereof with a harder type polyepoxy.

The present invention may be further understood by reference to thefollowing examples which are not to be construed as limiting.

EXAMPLE 1 A solution of 26 parts of a clear, transparent styrene maleicanhydride copolymer containing 20 weight percent maleic anhydride, 9parts of the diglycidyl ether of Bisphenol A having an average molecularweight of 340 and parts of methyl ethyl ketone was prepared. Thissolution had an absolute viscosity of about 200 c.p.s. Glass panels werecoated with the solution and baked in an oven at 200 C. After 15minutes, the films were insoluble in methyl ethyl ketone, and stablewhen immersed in water for 2 days. When coated on a tin-plated steelpanel and baked at 150 C. for 4 hours, the film was glossy, stable inwater for more than 4 months, crazed but did not fail when bent around aA1 inch mandrel and showed no failure on concave impact test at 10 inchpounds.

EXAMPLE 2 N-methyl morpholine, 1.5 weight percent based oncopolymer-epoxy resin, was added to a portion of the solution preparedin Example 1. The resulting solution was spread on glass panels andbaked at 200 C. for 5 minutes. The film was insoluble in methyl ethylketone.

EXAMPLE 3 The experiment of Example 2 was repeated using triethylaminein place of the N-methyl morpholine. After curing for 10 minutes, thefilms were insoluble in methyl ethyl ketone.

EXAMPLE 4 A series of copolymers having the composition as indicated inthe following table were prepared by the continous coil copolymerizationmethod of copending application S.N. 33,376, filed June 2, 1960. In thatmethod, a ketone solvent in an amount of 5 to 50 weight percent based ontotal non-polymeric constituents in the reactor, is employed to producea homogeneous solution from which clear and homogeneous copolymers areobtained. These copolymers were then dissolved in methyl ethyl ketonewith an amount of a polyepoxide necessary to provide the indicatedepoxide to anhydride ratio and with 03 weight ercent of Arquad 12 (a 50percent alcohol solution of dodecyl trimethyl ammonium chlorides) ascatalyst. The solutions were evaporated overnight and then cured at 160C. for one hour. The films had good clarity and cure, as measured byinsolubility in methyl ethyl ketone. They were of fair to good hardness.

The polyepoxides employed in these compositions were DER332 diglycidylether of Bisphenol A; Epon 812 (a product having an epoxide equivalentweight of -165, an average molecular weight of 3-00 and a viscosity at25 C. of 150-210 c.p.s.); the diglycidyl ether of a polypropylene glycolhaving an average molecular weight of about 400 and an epoxideequivalent weight of about 355 (herein designated as Epoxy 355);3,4-epoxy-6-methylcyclohexylmethyl-3, 4-epoXy-6-methylcyclohexanecarboxylate (Unox 201); Oxiron 2001 (a product having an epoxideequivalent weight of and an iodine number of 154); Epoxol 7-4 (anepoxidized soybean oil having an epoxide equivalent weight of 240 withan average of 4 epoxide groups per molecule); Cardolite NC 5-13 (anepoxidized cashew nut oil having an epoxide equivalent weight of475-575); DEN-438 epoxy novolac having a molecular weight of 600 and anepoxide equivalent weight of 17 6; and X2633.8 an epoxidized Bisphenol Ahaving an epoxide equivalent weight of 29 8.

All of the indicated copolymers were individually cured with Epoxy 355,Epon 812, Unox 201, 3,4-epoxy-6-methylcyclohexylmethyl acetate,2,3-epoxy-2-ethylhexanol and allyl-9,l0-epoxystearate. The remainingpolyepoxides were individually employed as curing agents as indicated inthe table.

TABLE I Wt. Polymer, Viscosity Ratio of Run percent wt. 10% epoxide toPolyepoxide curing agent maleic percent MEK anhydride anhydride styrene25 C.

1 5. 83 94. 17 7. 5 0.85 X2633.8/Epox01 7-4/Oxir0n 2G01/Cardolite NC513.

2 8. 26 91. 74 6. 9 0. 85 X2633.8/Cardolite NC513.

3 8 85.2 4. 7 0.85 X2633.8/Epoxol 7-4/Oxiron 2001/Cardolite N 0513.

4 19. 9 80. 1 4. 2 0. 85 X2633.8/Epx0l 7-4/Oxiro11 ZOOI/Cardolite NC513.

5 32. 4 67. 6 3. 4 X2633.8/Epoxol 7-4/Oxiron 2001/Ga1'd0lite NC513.

EXAMPLE 5 EXAMPLE A copolymer of 13.5 weight percent maleic anhydrideand 8 6.5 weight percent of vinyltoluene was prepared as in Example 4.Ten gram portions of this copolymer were dissolved in xylene withvarying amounts of 'DER332 epoxy resin to provide epoxide to anhydrideratios of 2.0, 1. 67, 1.43, 1.25, 1.11, and 1. 0; and 0.3 weight percentof Arquad 12. Films were cast from the solution on 10 mil tin plate testpanels and cured at 150 C. for one hour. The films were of good clarityand had good xylene resistance. They were resistant to marring,exhibited good adhesion and on a reverse impact test of 30 inch pounds,the films adhered tenaciously.

EXAMPLE 6 A series of acid and hydroxy polyesters was prepared byreacting 5 moles of adipic acid with 4 moles of glycerine, 3 moles ofadipic acid with 4 moles of glycerine, 2 and 3 moles of adipic acid with3 and 2 moles of ethylene glycol, respectively, and 5 moles of ethyleneglycol with 4 moles of phthalic anhydride. These polyesters plus dodecylsuccinic anhydride. Thiokol LP-3 (liquid polysulfide), polyglycol E600,and trimetallic anhydride were employed individually as additives inDER-332 epoxy resin modified styrene-maleic anhydride copolymers inquantities of from 4.6 to 45.8 weight percent, based on total weight ofcopolymer-l-DER332 epoxy resin additive. Films were cast from atoluene-methyl ethyl ketone solvent (1/ l) and cured for 75 minutes at160 C. The films were of good clarity, fair to good impact resistanceand had good resistance to marring.

EXAMPLE 7 In a manner similar to that of Example '6, a series ofcompositions containing non-reactive additives such as[2-2'(2-ethylhexanamido) diethyl-di-2-ethylhexoate], nbutyl stearate,dioctyl diphenyl oxide, tris butyl phenyl phosphate, and low molecularweight poly-wmethyl styrene were prepared. These films were of goodcolor, clarity, and mar resistance and did not peel when immersed inacetone.

EXAMPLE 8 A copolymer of 324 grams of dichlorostyrene and 36 grams ofmaleic anhydride was prepared by refluxing in methyl ethyl ketone forhours in a nitrogen atmosphere using azo-bis-isobutyronitrile as acatalyst. The viscosity (10% in MEK) was 0.66 cps. A compositioncontaining 10 grams copolymer, 2.15 grams DER332 epoxy resin, 0.091 ml.of Arquad 12 and 0.664 gram of dodecyl succinic anhydride was cast fromMEK and baked at 160 C. for 70 minutes. The films had good color andclarity and were resistant to marring. They did not swell or peel inacetone.

EXAMPLE 9 25 grams of the copolymer of Run 3 of Example 4 were dissolvedin dry acetone and 2.5 grams of styrene oxide were added. The solutionwas evaporated overnight in an open dish and then baked at 100 C. forone hour. The resulting product was insoluble in MEK and was transparentand hard.

A copolymer of weight percent dichlorostyrene and 10 weight percentmaleic anhydride, prepared as in Example 4, was dissolved in acetone to40 percent solids. There were then added 35.5 parts of DER332 epoxyresin per parts of copolymer and 0.5 weight percent, based on totalsolids, DMP30 solids. The resulting mixture was thinned to 40 percentsolids with MEK.

Glass cloth (weave style 181 with Volan A finish) was saturated withthis solution by repeated dipping and allowed to air dry for 1 /2 hoursfollowed by oven drying at F. for 5 minutes. The final weight ratio ofglass to resin was 52.5/47.5.

Twelve plys of the treated cloth were stacked in a fiat press at 300 F.After 15 seconds at 50 p.s.i., the pressure was raised to 400 p.s.i. for3 minutes, then 700 p.s.i. for 27 minutes. The laminate was cooled 5minutes. It was transparent, hard, strong, had good appearance and wasself-extinguishing in 5 seconds after removal from a flame source.

EXAMPLE 11 coating (1.1 mils) had excellent xylene and mar resistance.

EXAMPLE 12 A homogeneous copolymer of styrene and maleic anhydridecontaining 18.06 weight percent MA and having a solution viscosity of0.67 cps. (10% in MEK) was prepared by the continuous coilpolymerization method without recycle at 235 C. using a feed of 61.4weight percent styrene, 10.0 weight percent MA and 28.6 percent methylisobutyl ketone. The percent solids in the reactor was 71.4 and theproduct solution was devolatiliz/ed at 250 C. yielding on grinding afine white powder containing 6.5% volatiles. Six grams of this powderwere dissolved in aqueous ammonia to form about a 15% solids solution ata pH of 7 to 8 and 2.7 g. of Dowanol TBH butyl ether (T riethyleneglycol mono butyl ether and higher having an OH equivalent weight of240) and 1.9 g. of DER332 epoxy resin were added. Upon mixing, an opaquebut stable dispersion was formed that was readily cast on a tin platetest panel. After air drying the coating was baked at C. for 30 minutesresulting in a mar resistant, acetone insoluble, clear protectivecoating which was unefiected by 4 hours immersion in a steam bath.Similar results were obtained with a polymer containing 23% MA.Similarly, 2-methylpentanediol-3,4 and polyglycol P600 were substitutedin equivalent amounts for the Dowanol TBH butyl ether with the resultingcoatings exhibiting similar properties of mar resistance, acetoneinsolubility and water insensitivity.

EXAMPLE 13 To illustrate the near equimolarity of styrene-maleicanhydride copolymers prepared by the prior art methods,

7 Example VII of US. Patent 2,530,983 to H. F. Minter was repeated asfollows:

A charge of: 28.98 grams maleic anhydride, 17.22 grams maleic acid,153.80 grams styrene, 200.00 grams acetone, and 1.34 grams t-butylperbenzoate was mixed at room temperature for about an hour and thenheated to reflux. After heating at reflux for three hours, 300 grams ofacetone was added to cool the mixture and prevent furtherpolymerization.

(A) 278 grams of the resulting syrup was poured into about 3000 grams ofSkellysolve 60-70 C., and the precipitate was removed by filtration,washed with dry ether and air dried. A portion of this product wasdevolatilized at 190 C. for 2 hours under vacuum and a 16.9 gram sampleof the devolatilized product was dissolved in 200 grams methyl isobutylketone and fractionally precipitated with Skellysolve 60-70 C. Theresults were as follows:

The maleic anhydride content was determined by titration with alcoholicKOH and was checked by infrared analysis which indicated less thanmaleic acid present.

(B) 49.82 grams of the syrup were poured into about 1000 grams ofdiethyl ether, the resulting precipitate removed by filtration and ovendried for 3 days at 60 C. The product weighed 3.5 grams and titrated4.76 meq. KOH per gram. Infrared indicated less than 5% maleic acidpresent. Assuming the maleic moiety is all anhydride, the weight percentanhydride in the copolymer was 46.7, i.e., the polymer contained 1.87grams styrene and 1.63 grams maleic anhydride. The percent conversionwas 24.6%. Thus, this sample contained about 8.03 grams of unreactedstyrene plus about 0.42 gram maleic anhydride and 1.23 grams maleic acidor about 16% of the remaining monomer was the maleic moiety whereas inthe initial starting mixture the maleic coiety constituted percent ofthe monomer.

Various modifications may be made in the present invention withoutdeparting from the spirit or scope thereof and it is understood that welimit ourselves only as defined in the appended claims.

We claim:

1. A clear, thermosetting coating composition comprising (A) ahomogeneous copolymer of (1) from 99 to 65 weight percent of vinylaromatic compound, (2) from 1 to weight percent of an a ti-unsaturateddicarboxylic acid or anhydride, said copolymer having a distributionsuch that at least 90 percent of the copolymer will have an unsaturatedanhydride component composition which does not vary more than 5 percentand (B), an epoxide having an epoxide equivalent weight of between 44and 1000, in a ratio to the vinyl aromatic copolymer such that theepoxide to anhydride, including anhydride plus COOH, ratio is between0.2 and 2.5.

2. Composition of claim 1 wherein the vinyl aromatic copolymer comprisesat least 60 weight percent of said composition.

3. Composition of claim 2 wherein the vinyl aromatic copolymer containsfrom 97 to weight percent of the vinyl aromatic compound, and,correspondingly, from 3 to 20 weight percent or": an c p-unsaturateddicarboxylic acid or anhydride.

4. Composition of claim 1 wherein the vinyl aromatic copolymer has amolecular weight, characterized by 10 percent solution viscosity inmethyl ethyl ketone by 25 C. of 0.5 to 20 cps.

5. Composition of claim 1 wherein the epoxide has an epoxide equivalentweight of between 70 and 550.

6. Composition of claim 1 wherein the epoxide is a glycidyl ether of apolyhydroxy phenol having an epoxide equivalent weight of from to 550.

7. Composition of claim 1 wherein the epoxide to anhydride ratio isbetween 0.5 and 2.0.

8. Composition of claim 1 wherein the cap-unsaturated dicarboxylic acidanhydride is maleic anhydride.

9. Composition of claim 8, wherein the vinyl aromatic compound isstyrene.

10. Composition of claim 9, wherein the epoxide is the diglycidyl etherof Bisphenol A.

1].. Composition of claim 1, contained in an organic solvent therefor.

12. Composition of claim 11, wherein the solvent comprises a majorproportion of xylene.

13. A method of coating an article comprising applying to a surface ofthe article the composition of claim 1 and thereafter curing saidcomposition.

14. An article having on at least one surface a thin, tough continuousand adherent baked on coating consisting essentially of the compositionof claim 1.

15. A laminate structure comprising at least two lavers joined togetherby and integrally bound with, a tough, adherent, cured adhesiveconsisting essentially of the composition of claim 1.

16. Method of preparing coating and adhesive compositions comprisingcombining a homogeneous copolymer of from 99 to 65 weight percent of avinyl aromatic compound and 1 to 35 weight percent of ana,fl-unsaturated dicarboxylic acid or anhydride with an epoxy compoundin an amount such that the epoxide to anhydride plus COOH ratio is from0.2 to 2.5.

References Cited UNITED STATES PATENTS 2,604,464 7/1952 Segall et al.260-805 2,949,438 8/1960 Hicks 260836 3,046,246 7/1962 Muskat 2608363,136,136 6/1964 Washburne et a1. 260837 OTHER REFERENCES A. W. Hansonand R. L. Zimmerman, Ind. & Eng. Chem., 49 (11), November 1957; pp.1803-1806.

MORRIS LIEBMAN, Primary Examiner.

I. E. CALLAGHAN, Assistant Examiner.

US. Cl. X.R.

